1. Technical Field
The present invention relates to a manufacturing apparatus of an optical device, a manufacturing method thereof and a projector.
2. Related Art
There has been known a projector that includes an optical device and a projection optical device (projection lens), the optical device having three optical modulators (liquid crystal panels) that respectively modulate each of three color lights (R, G, B) in accordance with image information and a color-combining optical device (cross dichroic prism) that has the optical modulators and combines three modulated light beams to form an image light, and the projection optical device projecting the formed image light in an enlarged manner.
In the above projector, the liquid crystal panels need to be at back-focus positions of the projection lens in order to obtain a clear image. To make the image clearer, it is further necessary to prevent pixel displacement among the liquid crystal panels.
To meet these requirements, a focus adjustment for accurately positioning the liquid crystal panels at the back-focus positions of the projection-lens and an alignment adjustment for aligning pixels of the liquid crystal panels are precisely performed in the manufacturing process of the projector. And a manufacturing apparatus of an optical device that manufactures the optical device by performing such adjustments has been known (see, for instance, JP-A-2000-147448).
The manufacturing apparatus of the optical device disclosed in the above patent publication includes: an adjustment light-source device for introducing a light beam to liquid crystal panels; a light-beam detector for detecting the light beams having passed through the liquid crystal panels and a cross dichroic prism; and position-adjusting devices for performing the focus and alignment adjustments of the liquid crystal panels.
In the focus adjustment performed by the manufacturing apparatus, while the liquid crystal panels are moved respectively in a direction toward and away from the cross dichroic prism, the light beams having passed through the liquid crystal panels and cross dichroic prism are detected respectively at several positions in the direction. For each detected image, luminance values are calculated at several positions in order to FIG. 10 out variations in the luminance values (a dispersion value of the luminance). The position of the liquid crystal panel corresponding to the image of which dispersion value of the luminance is the largest among the plurality of images, i.e., the image with the highest contrast is determined as a focus position.
However, in the focus adjustment performed in the manufacturing apparatus disclosed in the above patent publication, the light beams having passed through the liquid crystal panels and cross dichroic prism need to be detected at many positions in the direction toward and away from the cross dichroic prism, and the focus position of the liquid crystal panels is determined based on the many detected images. Accordingly, the adjustment requires a long time for respectively moving the liquid crystal panels to the positions to detect the images as well as for determining the focus position based on the many images, which impedes speedy manufacturing of the optical device.